EncounterSettings

Changes CVars when a boss encounter starts and puts them back when it ends.

/es set 3420 graphicsParticleDensity 0    hide particle effects on Sszorak (encounter 3420)
/es unset 3420 graphicsParticleDensity    clear that setting
/es clear 3420                            clear every setting for Sszorak
/es set graphicsParticleDensity 0         leave out the ID to use the last boss you pulled
/es                                       show all settings and the ID of the last boss you pulled

Any CVar the client lets you change will work. Inside a raid with 'Raid & Battleground' settings enabled, the RAID twin of a CVar is used instead (raidGraphicsParticleDensity for graphicsParticleDensity, RAIDfarclip for farclip), so configure the base name. Two useful ones:

• graphicsParticleDensity: 0 (disabled) to 5 (ultra)
• graphicsViewDistance: 0 to 9, shown as 1 to 10 in the options panel

The wiki's complete list of console variables has the other graphics settings.